Ancient Japanese staple and supposed superfood, Natto gets a lot of hype for something
that looks like beans swimming in slimy pond scum.
Fermenting soybeans using bacteria creates something slimy and sticky, but also funky
and savory -- and, some people believe, based on a growing body of evidence, pretty good for you.
Natto is often eaten in Japan as a high-protein breakfast food.
Just add some soy sauce, maybe a little mustard, green onions or raw egg yolk and serve over
rice -- like we did here.
It’s pungent, by which I do mean stinky, and is often compared to washed rind cheese in terms of its complex funkiness
and in-your-face-ness.
When I tried it, I got strong notes of both cheese and coffee -- which don’t seem like they’d go well together.
It’s an acquired taste, but I can see how you’d go about acquiring it -- it’s actually really interesting!
In fermentation, you use microbes that grow and actually kind of pre-digest your food
to create new and interesting changes in the flavor, the smell, the mouthfeel and even nutritional content.
But you only want specific, friendly microbes setting up camp.
You don’t want others in there that could cause the food to spoil.
To transform soybeans into natto, makers use a particular strain of the bacterium B. subtilis,
a common soil-dwelling bacterium with some neat tricks up its sleeve.
When B. subtilis are facing stress from their environment, they have an escape plan— they
can start forming dormant cells housed in super-tough armor called spores.
Spores aren’t really alive; they’re kind of like seeds of a plant but they're practically indestructible.
They’re resistant to extreme temperatures, corrosive chemicals, and even radiation.
And they don’t need food or water.
So you can cook your soybeans at temperatures and pressures that would kill most other microbes
that might be around.
Then you introduce B. subtilis spores while the soy beans are still hot, and those Bacillus spores
are the only thing that can stand to be in there.
After that, your natto-to-be is held in hot, humid conditions for about a day or so
to allow the bacteria to settle in and get to work.
Since no one else is home, B. subtilis spores wake up and have no absolutely competition
to eat the lovely beans.
And the effect of its munching is to transform the bland unfermented soybeans into...THIS.
But why do the bacteria produce these gooey strings?
Turns out this slippery substance is what microbiologists called a biofilm — a protective
environment for the bacteria to live in, something lots of bacteria make for themselves.
This particular biofilm is made primarily of polyglutamate.
The amino acid glutamate is responsible for the flavor of savoriness -- these strings
shed glutamate molecules, which our tongues perceive as umami.
More umami flavor emerges in the Natto over time as the biofilm produces more glutamate molecules.
Protected by this biofilm, the bacteria go to town chowing down on the carbs & proteins of the beans.
The fermentation of natto takes place above pH 7 -- it’s an alkaline-fermented food.
A lot of other fermented foods are actually acidic, which makes them taste sour.
That’s probably why I went in expecting the natto to taste like yogurt or something, but instead
it had a more earthy, slightly bitter flavor that reminded me of coffee or truffles..
Like a lot of fermented foods, natto was likely “discovered” by accident and turned out
to be a good way to preserve soybeans.
But it’s still best fresh, as opposed to frozen.
And since it will slowly keep fermenting in your fridge, after a while, it can get pretty strong.
There’s also a lot of buzz surrounding the health benefits of natto.
The label “superfood” is usually more hype than substance, but scientists have taken
an interest in natto and what it might do for us.
For example, natto is the most potent food source of vitamin K2, a micronutrient that
helps build bone by transporting calcium from your bloodstream to your bones.
And B. subtilis is found in healthy human guts, so eating natto might have probiotic effects.
Natto also contains nattokinase, an enzyme made by B. subtilis, that’s been shown both
in the lab and in humans to have potentially useful effects as a blood thinner and therefore
in fighting heart disease.
It supposedly works by breaking down blood clots, so they can’t get stuck in your arteries
and cause a heart attack or stroke.
Human trials are still ongoing into the effects of nattokinase, in heart disease as well as
things like Alzheimer’s.
We definitely don’t know everything about nattokinase yet, like how or whether it’s
actually absorbed by the body, and whether it might interfere with other drugs.
But doctors are keeping an eye on this one.
That said, natto doesn't have to be a health food to be worth eating.
You can just enjoy the slimy funkiness.
Which I sort a did. Let's be real. I'll give it another shot sometime.
We want to give a huge shoutout and thanks to Ann Yonetani of NYrture Foods.
Who, when we reached out about potentially fact-checking an episode,
was so thrilled she sent us a bunch of free natto and Instagram resources and images and all kinds of great stuff!
Thanks so much Ann.
Thanks for watching and thank you Paul Smith and Chelsea Conlin for asking about natto.
Drop your food chemistry questions in the comments. We love these ideas so we’ll see if we can take them on.
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